8mm Mauser 125 gr jacket bullet load

[rayg]

I have a MP 44 in 7.92X33 cal. that I use the 125 gr jacketed 323 bullets in with 21.5 grs of I-4891 powder. Runs about 2100 ft per second and works the action well.
I want to try these same bullets in my 98K Mauser with light loads but all the books I have show high 2800 fps plus loads with mid 40 plus powder loads.
Does anyone shoot a milder load in their Mausers with these bullets? Ray

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[Patrick Chadwick]

all the books I have show high 2800 fps plus loads with mid 40 plus powder loads.

I think there is a good reason for this. The minimum load must be able to press the bullet completely and reliably into the rifling in the throat so that it takes the rifling completely. This takes a certain minimum pressure, otherwise you may experience a plugged bore with all the consequences.

Once this deformation has taken place, any bore friction is insignificant by comparison, and that minimum pressure goes into accelerating the bullet. So it is not surprising that the mininum pressure required to force the bullet into the rifling (which will, of course, vary somewhat with the length of bullet in contact with the rifling) will give a smaller bullet more acceleration, so that it emerges faster.

In other words, whether or not someone chips in with "cat's sneeze" loads, please consider that underloading can be a problem, maybe even downright hazardous. I consider it prudent to assume that Messrs Hornady, Sierra, Vihtavuori et al have put some thought into their loading manuals.


Patrick

[rayg]

I understand the concern for using full power loads but I think it's more to expand the case into the chamber upon firing so there is no gas blow back and primer back out then it is to bump up the bullet into the rifling. As the same bullet with only 21.5 grs of I-4198 powder, (errored in 1st post calling it 4891 powder), in the same dia .323 bore in my MP44 works well of course the difference being the MP44 only has a 16.5 barrel and a much smaller case. The larger 8mm case may need more powder for more pressure to expand the case for gas seal in the chamber.

One of my reloading books give a load with the 4198 powder as 39 grs to 44 grs. If no one offers another light load, I'll just try the 39 gr min load and work my way down until the case fails to seal.
I have a number of other powders I can use, Ray

[vintage hunter]

Another concern when using light charges(especially those lighter than the minimum listed) in fairly large cases is the possibility of a flashover where the entire charge ignites at once instead of burning progressively. Some manuals recommend the use of some sort of filler to hold the charge to the rear of the case, but, unless noted don't use them. Don't be dissapointed if accuracy is below what your expecting, seldom do these old milsurps perform well with bullets lighter than those it was designed to shoot whilst in service.

[Patrick Chadwick]

to expand the case into the chamber upon firing so there is no gas blow back and primer back out

That is also true, of course. As to which effect makes itself noticeable first, well I suspect that is one of those "It all depends" problems. For instance, it depends on how fast the powder is. The case just requires a certain pressure to expand, but the bullet need a certain amount of dynamic "whack". A bit like hammering a nail into piece of wood - you might be able to practically stand on the nail all day long, i.e. apply a high steady pressure, without making much impression, but a short, sharp tap with a hammer will drive it into the wood - the kinetic energy of the hammer blow is transformed into a very brief period of very high pressure at the metal/wood boundary that is sufficient to part the wood fibers. Getting back to cartridge loading: the lighter the bullet, the faster the powder needs to be to produce that "whack". And, of course, if the charge is so weak that the case does not expand properly and there is gas blowback, then the driving force on the bullet will also be weakened.


Patrick

[Johnny Peppers]

The old Phil Sharpe Complete Guide to Handloading has light loads, but not with the 125 grain bullet. The lightest bullet he has is 154 grains, but shows it with an 11 grain load of Unique for a velocity of 1400 fps with 16,600 breech pressure. Another load that approached your velocity was 23.6 grains of 2400 for a velocity of 2030 fps at 28,000 breech pressure.

[Parashooter]

The general principle in developing loads like you're seeking is to use a powder that is both easy to ignite at low loading density and has a burning rate appropriate to give sufficient pressure for chamber obturation while delivering the reduced velocity you want. Easily-ignited powders include porous-base products like IMR's SR4759 and double-base extruded powders like Accurate 5744 and the Alliant products through RL-7. Avoid fine-grained extruded single-base powders (e.g. 4198) and all spherical powders - these can be difficult to ignite consistently at low density.

C.E. Harris's "The Load", with 13 grains of Red Dot is a proven place to start (~1800 fps). If you need more velocity, move up through 25+ of 4759 or 5477, on up to ~34 of RL-7 (~2500 fps).

An often-overlooked factor with short, light bullets is the need to seat them at least one caliber deep to give sufficient time for pressure to expand the case before the bullet leaves it.

[Patrick Chadwick]

C.E. Harris's "The Load", with 13 grains of Red Dot is a proven place to start (~1800 fps). If you need more velocity, move up through 25+ of 4759 or 5477, on up to ~34 of RL-7 (~2500 fps).

Thanks Parashooter for a practical example. The fast-burning pistol-type powder produces the "whack" to get the bullet seated in the rifling, and then the bullet can glide on down with comparatively little further drive/acceleration compared with a normal load, as the powder has already produced most of its energy. But the trouble will come if that short impulse is not enough. And the real hazard is that it is very easy to double load such small charges.

OK, so I'm an old wet. But having once had a plugged bore from commercial ammo in a 45-70, where the bullet stopped just far enough into the rifling that it would have been possible to load another round, I am very, very, very cautious. The miserable little charge of nitro powder had quite simply failed to ignite properly, and was still rattling around in the 45-70 case. I would like to remain in one piece at the range, and, as you have probably realized, regard Scrooge loads as an unnecessary risk.

I shall now shut up and go and load my cases with reasonable loads of moderately paced powder!


Patrick

[rayg]

Thanks for the responses. I did post this question on other several forums also. Some thoughts. I do cast bullets for my ZF41, K98 and get great results. However I have not shot my MP44 for a while because it's a bit inconvient because of distance I have to travel to the range that allows FA whereas I have a rifle range only 10 min from me that does not allow FA. But I do occassionaly shoot the MP44 semi at that rifle range but just thought that as I have a couple of boxes of the little 125 grainers just sitting gathering dust that I might try in the Mauser.
I found an old manual that suggests 39-44 grs, I-4198 for that little pill.
I believe, and of course this is just my opinion, that it doesn't take much pressure to shoot that small bullet having a minimun bore ride length through the bore. For one thing, if the pressure is too low, the bullet won't bump up into the rifling, which means even less resistance.
The thing I need to be concerned about is to get enough pressure to fully expand the case in the chamber to avoid gas blow back and primer backout.
I may just start with the min of 39 grs and maybe work down until there is blow back. Of couse that will all depend on accuracy. I also could try 2400 or Red Dot powder that I have. The 2400 is not position sensitive and might be the best one to use. I use it with my cast bullets.
I'm just curious just how light I can get the load. I will of course make sure with any load that no bullet remains in the bore. Ray

[Parashooter]

None of the load levels I mentioned above are anywhere near the "stuck in the bore" category. Rather, they are in the 17-30,000 psi range where we can expect effective chamber obturation with good brass. In addition, none of them are below 46% loading density (with bullet seated at least .32") and would require a dismal level of inattention to allow loading a double charge.



Graph below shows simulations of ~27,000 psi loads with Red Dot and 4198. Which to try depends on the velocity level desired. For paper targets at 100-200 yards, ~1800 fps is normally plenty.